running on this tax plan. and now, five weeks before the election, he's saying that his big bold idea is never mind. >> let me repeat what i said. i'm not in favor of a $5 trillion tax cut, that's not my plan. >> reporter: another stark difference, medicare, one of the few times the president played aggressor. >> it's called premium support, but it's understood to be a voucher program. >> and you don't support that? >> i don't. and let me explain why. >> again, that's for future people, not current retirees. >> so if you're 54 or 55, you might want to listen because this, this will affect you. >> reporter: still, romney seemed to control many of the back and forths, even the lighter moments. >> i apologize, mr. president, i use that term with all respect. >> i like it. >> good. >> the difference in their debate demeanors was most evident during the closing statements. >> you know, four years ago we were going through a major crisis. and yet, my faith and confidence in the american future is undiminished. >> th